2018-12-rails-5.0-upgrade

Goals based on upgrade page: https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-4-2-to-rails-5-0

4.1 Ruby version: We're already good at 2.4.  Might consider going to 2.5, but no urgency.

4.2 Introduce ApplicationRecord.
- Search for ActiveRecord::Base.
- Ensure that all classes inherit from ApplicationRecord
- Add definition per web page

4.3 Halting Callback Chains: Don't think this is relevant to anything we're doing, but we'll see.

4.4 ActiveJob: We don't use ActiveJob

4.5 Rails Controller Testing:
- Probably need to add the rails-controller-testing gem
- Already using Rack::Test::UploadedFile

4.6 Autoloading: Don't think is an issue for us, but doesn't appear to be a great ways to test it other than just running it in production

4.7 XML Serialization: Doesn't appear to affect our code

4.8 Remove legacy mysql adapter: Already using mysql2

4.9 Removed Support for Debugger: We're already using byebug

4.10 bin/rails instead of rake: Nothing to do here

4.11 ActionController::Parameters: Not sure how the permitted? stuff works so hard to tell but should surface in testing.

4.12 protect_from_forgery: Appears in one place in the code.  Hopefully tests will tell us whether this is a problem or not.

4.13 Default template handler in Now Raw: This might be an issue if we have any ERB files without the right suffix.

4.14 Wildcare Matching for Template Dependencies: Extension/feature - old code should "just work"

4.15 RecrodTagHelper: Not in our code base

4.16 protected_attributes: Not in our code base

4.17 activerecord-deprecated_finders: Not in our code base

4.18 Test Order is Now Random: We've been running that way for a long time.

4.19 ActionController::Live: Not in our code base

4.20 New Framework defaults
None of these look like big deals since it sounds like old project are generally going to get handled correctly automatically

4.21 JSON/JSONB serialization: Not clear if this is an issue or not.  Will have to see what the tests tell us.